The permanent magnetic moment of the atoms of a material is not zero. The material

Options

A. must be paramagnetic
B. must be diamagnetic
C. must be ferromagnetic
D. may be paramagnetic

Answer

To determine the type of material based on the information that the permanent magnetic moment of the atoms is not zero, we can analyze the characteristics of different types of magnetic materials: diamagnetic, paramagnetic, and ferromagnetic.

### Step-by-Step Solution:

1. **Understanding Magnetic Moments**:
- A magnetic moment is a vector quantity that represents the magnetic strength and orientation of a magnet or current loop. It is associated with the magnetic properties of materials.
- If the permanent magnetic moment of the atoms is not zero, it indicates that the material has unpaired electrons contributing to a net magnetic moment.

2. **Classifying Magnetic Materials**:
- **Diamagnetic Materials**: These materials have all their electrons paired. As a result, they do not have a permanent magnetic moment. When placed in a magnetic field, they develop a very weak magnetization in the opposite direction of the applied field. Examples include wood, water, and bismuth.
- **Paramagnetic Materials**: These materials have some unpaired electrons, which means they possess a permanent magnetic moment. When placed in a magnetic field, they align with the field, resulting in a net magnetization in the same direction as the applied field. Examples include aluminum and platinum.
- **Ferromagnetic Materials**: These materials also have unpaired electrons and possess a strong permanent magnetic moment. They can retain their magnetization even after the external magnetic field is removed. Examples include iron, cobalt, and nickel.

3. **Analyzing the Given Information**:
- Since the problem states that the permanent magnetic moment of the atoms is not zero, we can conclude that the material cannot be diamagnetic (as diamagnetic materials have no permanent magnetic moment).
- The material must either be paramagnetic or ferromagnetic, as both types have unpaired electrons contributing to a net magnetic moment.

4. **Conclusion**:
- Therefore, the material can be classified as either paramagnetic or ferromagnetic. However, since the question asks for the specific type of material based on the condition that the permanent magnetic moment is not zero, the most definitive conclusion is that the material must be **ferromagnetic**. This is because ferromagnetic materials have a strong permanent magnetic moment and can maintain magnetization.

### Final Answer:
The material must be **ferromagnetic**.